Spin current magnetization rotational element, magnetoresistance effect element and magnetic memory

ABSTRACT

This spin current magnetization rotational element includes a second ferromagnetic metal layer  1  having a variable magnetization orientation, and spin-orbit torque wiring  2 , which extends in a direction that intersects a direction perpendicular to the surface of the second ferromagnetic metal layer  1 , and is connected to the second ferromagnetic metal layer  1 , wherein the spin resistance of a connection portion of the spin-orbit torque wiring layer  2  that is connected to the second ferromagnetic metal layer  1  is larger than the spin resistance of the second ferromagnetic metal layer  1.

This is a divisional application of application Ser. No. 15/777,884,filed May 21, 2018, which claims priority on Japanese Patent ApplicationNo. 2015-232334, filed Nov. 27, 2015, Japanese Patent Application No.2016-53072, filed Mar. 16, 2016, Japanese Patent Application No.2016-56058, filed Mar. 18, 2016, Japanese Patent Application No.2016-210531, filed Oct. 27, 2016, and Japanese Patent Application No.2016-210533, filed Oct. 27, 2016, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a spin current magnetizationrotational element, a magnetoresistance effect element, and magneticmemory.

BACKGROUND ART

Giant magnetoresistance (GMR) elements composed of a multilayer film offerromagnetic layers and non-magnetic layers, and tunnelmagnetoresistance (TMR) elements which use insulating layers (tunnelbarrier layers, barrier layers) for the non-magnetic layers are alreadyknown. Generally, although TMR elements have a higher element resistancethan GMR elements, the magnetoresistance (MR) ratio of TMR elements islarger than the MR ratio of GMR elements. Consequently, TMR elements areattracting much attention as elements for magnetic sensors,high-frequency components, magnetic heads and non-volatile random accessmemory (MRAM).

Examples of known methods for writing to MRAM include a method in whicha magnetic field generated by an electric current is used to performwriting (magnetization rotation), and a method in which a spin transfertorque (STT) generated by passing an electric current through thestacking direction of a magnetoresistance element is used to performwriting (magnetization rotation).

In the method that uses a magnetic field, a problem arises in that whenthe size of the element is small, writing becomes impossible to performwith the size of the electric current that is able to flow through thefine wires.

In contrast, in the method that uses spin transfer torque (STT), oneferromagnetic layer (the fixed layer or reference layer) causes spinpolarization of the current, that current spin is transferred to themagnetization of the other ferromagnetic layer (the free layer orrecording layer), and the torque (STT) generated at that time is used toperform writing (magnetization rotation), and this method offers theadvantage that as the size of the element decreases, the size of thecurrent required for writing also decreases.

PRIOR ART LITERATURE Non-Patent Documents

-   Non-Patent Document 1: I. M. Miron, K. Garello, G. Gaudin, P.-J.    Zermatten, M. V. Costache, S. Auffret, S. Bandiera, B. Rodmacq, A.    Schuhl, and P. Gambardella, Nature, 476, 189 (2011).-   Non-Patent Document 2: T. Kimura, J. Hamrle, and Y. Otani, Phys.    Rev. B72(1), 014461 (2005).-   Non-Patent Document 3: S. Takahashi and S. Maekawa, Phys. Rev.    B67(5), 052409 (2003).-   Non-Patent Document 4: J. Bass and W. P. Pratt Jr., J. Phys. Cond.    Matt. 19, 183201 (2007).

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

Magnetization rotation of a TMR element using STT is efficient whenconsidered from an energy efficiency perspective, but the reversalcurrent density required to achieve magnetization rotation is high.

From the viewpoint of achieving a long life for the TMR element, thisreversal current density is preferably low. This point is similar forGMR elements.

Accordingly, in both types of magnetoresistance effect elements, namelyin both TMR elements and GMR elements, it is desirable to reduce thecurrent density that flows through the magnetoresistance effect element.

In recent years, magnetization rotation using pure spin currentgenerated by spin-orbit interaction has been advocated as a practicallyapplicable method (for example, Non-Patent Document 1). Pure spincurrent generated by spin-orbit interaction induces spin-orbit torque(SOT), and this SOT can cause magnetization rotation depending on themagnitude of the SOT. A pure spin current is generated when an electronwith upward spin and an electron with downward spin flow with the samefrequency in opposing orientations, and because the electric chargeflows cancel each other out, the resulting electric current is zero. Ifmagnetization rotation can be achieved using only this pure spincurrent, then because the electric current flowing through themagnetoresistance effect element is zero, the lifespan of themagnetoresistance effect element can be lengthened. Alternatively, it isthought that if STT is also used for magnetization rotation, then byusing SOT generated by pure spin current, the electric current used ingenerating the STT can be reduced by an amount equivalent to the amountof SOT generated by pure spin current, enabling a lengthening of thelifespan of the magnetoresistance effect element to be achieved. It isthought that in those cases where both STT and SOT are used, the greaterthe proportion of SOT that is used, the more effectively the lifespan ofthe magnetoresistance effect element can be lengthened.

Research into the use of SOT is really only just beginning, and it isthought that various problems will arise when SOT is used in specificpractical applications, but at present, even the types of problems thatmay arise are not fully understood.

Magnetization rotation using SOT is generated in a structure in which amember (for example, a layer or a film) formed from a material thatgenerates a pure spin current (hereafter also referred to as “the spincurrent generation member”) is connected to a ferromagnetic metal layerhaving a variable magnetization orientation (a free layer), bygenerating a pure spin current in the member by passing an electriccurrent through the member, and allowing that pure spin current todiffuse (be injected) into the ferromagnetic metal layer from theconnection portion between the member and the ferromagnetic metal layer.At this time, depending on the difference (mismatch) between the spinresistances of the spin current generation member and the ferromagneticmetal layer, the effect of the injected spin current returning from theferromagnetic metal layer into the spin current generation member issometimes a concern. This type of backflow spin current does notcontribute to rotation of the magnetization in the ferromagnetic metallayer. The present disclosure was discovered by investigating structureswhich reduce the amount of this type of backflow spin current.

The present disclosure has been developed in light of the above issues,and has an object of providing a magnetoresistance effect element andmagnetic memory that utilize magnetization rotation by pure spin currentin a state where backflow of the pure spin current from theferromagnetic metal layer (free layer) into the spin-orbit torque wiringis reduced.

Means for Solving the Problems

In order to achieve the above objects, the present disclosure providesthe following aspects.

(1) A spin current magnetization rotational element according to oneaspect of the present disclosure includes a second ferromagnetic metallayer having a variable magnetization direction, and spin-orbit torquewiring which extends in a direction that intersects a directionperpendicular to the surface of the second ferromagnetic metal layer,and is connected to the second ferromagnetic metal layer, wherein thespin resistance of a connection portion of the spin-orbit torque wiringthat is connected to the second ferromagnetic metal layer is larger thanthe spin resistance of the second ferromagnetic metal layer.(2) In the spin current magnetization rotational element according to(1) above, the spin-orbit torque wiring layer may have a spin currentgeneration portion formed from a material that generates a spin current,and a conductive portion, wherein a portion of the spin currentgeneration portion constitutes the connection portion.(3) In the spin current magnetization rotational element according to(2) above, the electrical resistivity of the conductive portion may benot higher than the electrical resistivity of the spin currentgeneration portion.(4) In the spin current magnetization rotational element according to(2) or (3) above, the spin current generation portion may be formed froma material selected from the group consisting of tungsten, molybdenum,niobium, and alloys containing at least one of these metals.(5) In the spin current magnetization rotational element according toany one of (1) to (4) above, the spin-orbit torque wiring may have aside wall connection portion that contacts a portion of a side wall ofthe second ferromagnetic metal layer.(6) A magnetoresistance effect element according to one aspect of thepresent disclosure includes the spin current magnetization rotationalelement according to any one (1) to (5) above, a second ferromagneticmetal layer having a fixed magnetization orientation, and a non-magneticlayer sandwiched between the first ferromagnetic metal layer and thesecond ferromagnetic metal layer.(7) In the magnetoresistance effect element according to (6) above, thefirst ferromagnetic metal layer may be positioned below the secondferromagnetic metal layer in the stacking direction.(8) Magnetic memory according to one aspect of the present disclosurecontains a plurality of the magnetoresistance effect elements accordingto (6) or (7) above.

A magnetization rotation method is a method for reversing themagnetization in the magnetoresistance effect element according to (6)or (7) above, wherein the electric current density flowing through thespin-orbit torque wiring is set to less than 1×10⁷ A/cm².

Effects of the Invention

By using the spin current magnetization rotational element according tothe present disclosure, magnetization rotation using pure spin currentcan be performed in a state where backflow of the pure spin current fromthe ferromagnetic metal layer (free layer) into the spin-orbit torquewiring is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematically view for illustrating a spin currentmagnetization rotational element according to an embodiment of thepresent disclosure, wherein (a) is a plan view and (b) is across-sectional view.

FIG. 2 is a schematic view for describing the spin Hall effect.

FIG. 3 is a perspective view for describing non-local measurement usinga lateral spin valve structure.

FIG. 4 is a perspective view for describing the measurement ofelectrical resistivity using the four-terminal method.

FIG. 5 is a perspective view schematically illustrating amagnetoresistance effect element according to an embodiment of thepresent disclosure.

FIG. 6 is a schematic view for describing an embodiment of spin-orbittorque wiring, wherein (a) is a cross-sectional view, and (b) is a planview.

FIG. 7 is a schematic view for describing another embodiment ofspin-orbit torque wiring, wherein (a) is a cross-sectional view, and (b)is a plan view.

FIG. 8 is a schematic view for describing yet another embodiment ofspin-orbit torque wiring, wherein (a) is a cross-sectional view, and (b)is a plan view.

FIG. 9 is a schematic view for describing yet another embodiment ofspin-orbit torque wiring, wherein (a) is a cross-sectional view, and (b)is a plan view.

FIG. 10 is a schematic cross-sectional view illustrating a section cutthrough the yz plane of a magnetoresistance effect element according toan embodiment of the present disclosure.

FIG. 11 is a schematic cross-sectional view illustrating a section cutthrough the yz plane of a magnetoresistance effect element according toanother embodiment of the present disclosure.

FIG. 12 is a schematic cross-sectional view illustrating a section cutthrough the yz plane of a magnetoresistance effect element according toyet another embodiment of the present disclosure.

FIG. 13 is a perspective view schematically illustrating amagnetoresistance effect element according to an embodiment of thepresent disclosure.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present disclosure is described below in further detail, withappropriate reference to the drawings. The drawings used in thefollowing description may be drawn with specific portions enlarged asappropriate to facilitate comprehension of the features of the presentdisclosure, and the dimensional ratios and the like between theconstituent elements may differ from the actual values. The materialsand dimensions and the like presented in the following descriptions aremerely examples, which in no way limit the present disclosure, and maybe altered as appropriate within the scope of the present disclosure.The elements of the present disclosure may also include other layers,provided the effects of the present disclosure are retained.

(Spin Current Magnetization Rotational Element)

FIG. 1 is a schematic view of one example of a spin currentmagnetization rotational element according to an embodiment of thepresent disclosure. FIG. 1(a) is a plan view, and FIG. 1(b) is across-sectional view of a section cut along the line X-X that representsthe centerline in the width direction of spin-orbit torque wiring 2 ofFIG. 1(a).

In a spin current magnetization rotational element according to oneaspect of the present disclosure, a spin current magnetizationrotational element 101 illustrated in FIG. 1 has a second ferromagneticmetal layer 1 having a variable magnetization orientation, andspin-orbit torque wiring 2, which extends in a second direction (thex-direction) that intersects a first direction (the z-direction) that isperpendicular to the surface of the second ferromagnetic metal layer 1,and is connected to a first surface 1 a of the second ferromagneticmetal layer 1, wherein the spin resistance of at least a connectionportion of the spin-orbit torque wiring 2 that is connected to thesecond ferromagnetic metal layer 1 is larger than the spin resistance ofthe second ferromagnetic metal layer 1.

The connection between the spin-orbit torque wiring 2 and the secondferromagnetic metal layer 1 may be a “direct” connection, or may involveconnection “via another layer” such as the cap layer described below,and there are no restrictions on the way in which the spin-orbit torquewiring and the second ferromagnetic metal layer are connected (joined orbonded), provided the pure spin current generated in the spin-orbittorque wiring 2 can flow into the second ferromagnetic metal layer 1.

A ferromagnetic material, and particularly a soft magnetic material, canbe used as the material for the second ferromagnetic metal layer 1.Examples of materials that may be used include metals selected from thegroup consisting of Cr, Mn, Co, Fe and Ni, alloys containing at leastone of these metals, and alloys containing at least one of these metalsand at least one element among B, C and N. Specific examples includeCo—Fe, Co—Fe—B and Ni—Fe.

In those cases where the orientation of the magnetization of the secondferromagnetic metal layer 1 is perpendicular to the stacking surface,the thickness of the second ferromagnetic metal layer is preferably notmore than 2.5 nm. In the magnetoresistance effect element describedbelow, perpendicular magnetic anisotropy can be applied to the secondferromagnetic metal layer 1 at the interface between the secondferromagnetic metal layer 1 and a non-magnetic layer 22 (see FIG. 5).Further, because the perpendicular magnetic anisotropy effect isattenuated as the thickness of the second ferromagnetic metal layer 1 isincreased, the thickness of the second ferromagnetic metal layer 1 ispreferably kept thin.

<Spin-Orbit Torque Wiring>

The spin-orbit torque wiring extends in a direction that intersects adirection perpendicular to the surface of the second ferromagnetic metallayer. The spin-orbit torque wiring is connected electrically to a powersupply that supplies an electric current to the spin-orbit torque wiringin a direction orthogonal to a direction perpendicular to the surface ofthe second ferromagnetic metal layer (namely, in the direction ofextension of the spin-orbit torque wiring), and functions, incombination with the power supply, as a spin injection device theinjects a pure spin current into the second ferromagnetic metal layer.

The spin-orbit torque wiring is formed from a material that generates apure spin current by the spin Hall effect when a current flows throughthe material. This material may have any composition capable ofgenerating a pure spin current in the spin-orbit torque wiring.Accordingly, the material is not limited to materials formed from simpleelements, and may also be composed of a portion formed from a materialthat generates a pure spin current and a portion formed from a materialthat does not generate a pure spin current.

The spin Hall effect is a phenomenon wherein when an electric current ispassed through a material, a pure spin current is induced in a directionorthogonal to the orientation of the electric current as a result ofspin-orbit interactions.

FIG. 2 is a schematic view for describing the spin Hall effect. Themechanism by which a pure spin current is generated by the spin Halleffect is described below based on FIG. 2.

As illustrated in FIG. 2, when an electric current I is passed along thedirection of extension of the spin-orbit torque wiring 2, anupward-directed spin S⁺ (S1) and a downward-directed spin S⁻ (S2) areeach bent in directions orthogonal to the electric current. The normalHall effect and the spin Hall effect have in common the fact that thedirection of travel (movement) of the traveling (moving) electric charge(electrons) is bent, but differ significantly in terms of the fact thatin the common Hall effect, charged particles traveling through amagnetic field are affected by Lorentz forces, resulting in a bending ofthe travel direction, whereas in the spin Hall effect, despite nomagnetic field existing, the travel direction bends simply under theeffect of the movement of the electrons (flow of current).

In a non-magnetic material (a material that is not ferromagnetic), theelectron count of the upward-directed spin S⁺ and the electron count ofthe downward-directed spin S⁻ are equal, and therefore in FIG. 2, theelectron count of the upward-directed spin S⁺ that is heading in theupward direction and the electron count of the downward-directed spin S⁻that is heading in the downward direction are equal. Accordingly, theelectric current represented by the net flux of the electric charge iszero. This type of spin current that is not accompanied by an electriccurrent is called a pure spin current.

In contrast, when an electric current is passed through a ferromagneticmaterial, the fact that the upward-directed spin electrons and thedownward-directed spin electrons are bent in opposite directions is thesame as above. However, the difference in a ferromagnetic material isthat one of either the upward-directed spin electrons or thedownward-directed spin electrons are more numerous, resulting in theoccurrence of a net flux for the electric charge (and the generation ofa voltage). Accordingly, a material formed solely from a ferromagneticsubstance cannot be used as the material for the spin-orbit torquewiring.

If the electron flow of the upward-directed spin S⁺ is represented byJ_(↑), the electron flow of the downward-directed spin S⁻ is representedby J_(↓), and the spin current is represented by J_(S), then the spincurrent is defined as J_(S)=J_(↑)−J_(↓). In FIG. 2, the pure spincurrent J_(S) flows in the upward direction in the figure. Here, J_(S)is an electron flow having 100% polarizability.

In FIG. 2, when a ferromagnetic material is brought into contact withthe upper surface of the spin-orbit torque wiring 2, the pure spincurrent diffuses and flows into the ferromagnetic material.

In the present disclosure, by employing a structure in which an electriccurrent is passed through the spin-orbit torque wiring in this manner togenerate a pure spin current, and that pure spin current then diffusesinto the second ferromagnetic metal layer that contacts the spin-orbittorque wiring, the spin-orbit torque (SOT) effect generated by this purespin current is able to contribute to magnetization rotation of thesecond ferromagnetic metal layer that represents the free layer.

The magnetoresistance effect element of the present disclosure describedbelow, namely a magnetoresistance effect element in which the SOT effectgenerated by pure spin current is used to achieve magnetization rotationof a ferromagnetic metal layer, can be used as an assist element thatuses the SOT effect generated by the pure spin current to assistmagnetization rotation that utilizes conventional STT, or as the mainelement for performing magnetization rotation using the SOT effectgenerated by the pure spin current with assistance from magnetizationrotation using conventional STT, or can also be used as a novelmagnetoresistance effect element in which magnetization rotation of theferromagnetic metal layer is conducted solely by the SOT generated bythe pure spin current.

Examples of known methods for assisting magnetization rotation includemethods in which an external magnetic field is applied, methods in whicha voltage is applied, methods in which heating is included, and methodsthat utilize strain in a substance. However, in the case of methods inwhich an external magnetic field is applied, methods in which a voltageis applied, and methods in which heating is included, additionalexternal wiring and heat sources and the like must be provided, therebyincreasing the complexity of the element structure. Further, in the caseof methods that utilize strain in a substance, once the strain has beengenerated, controlling that strain during use is difficult, andachieving magnetization rotation with good control is impossible.

In the spin current magnetization rotational element of the presentdisclosure, the spin resistance of at least the connection portion ofthe spin-orbit torque wiring that is connected to the secondferromagnetic metal layer is larger than the spin resistance of thesecond ferromagnetic metal layer. By using such a structure, when spincurrent diffuses from the spin-orbit torque wiring and is injected intothe second ferromagnetic metal layer, return of the spin current fromthe second ferromagnetic metal layer back into the spin-orbit torquewiring is reduced.

(Spin Resistance, Spin Resistivity)

The spin resistance is a value that quantitatively indicates the ease ofspin flow (the difficulty of spin relaxation). Non-Patent Document 2describes a theoretical treatment of spin resistance. At an interfacebetween substances having different spin resistance, reflection (return)of the spin flow can occur. In other words, only a portion of the spincurrent is injected from a material having a small spin resistance intoa material having a large spin resistance.

The spin resistance R_(S) is defined by the formula below (seeNon-Patent Document 3).

$\begin{matrix}\left\lbrack {{Numerical}\mspace{14mu} {formula}\mspace{14mu} 1} \right\rbrack & \; \\{R_{S} \equiv \frac{\rho\lambda}{A}} & (1)\end{matrix}$

In the formula, λ represents the spin diffusion length of the material,ρ represents the electrical resistivity of the material, and Arepresents the cross-sectional area of the material.

In a non-magnetic material, if the cross-sectional area is constant,then within the formula (1), the value of ρλ, which represents the spinresistivity, determines the size of the spin resistance.

Accordingly, in the spin current magnetization rotational element of thepresent disclosure, if the size of the spin-orbit torque wiring isconstant, then using a material having a large spin resistivity has agreater effect in reducing backflow of the spin current.

In the spin current magnetization rotational element of the presentdisclosure, in those cases where the second ferromagnetic metal layer isformed from iron (Fe) or an iron-based alloy, the spin resistance of atleast the connection portion of the spin-orbit torque wiring layer thatis connected to the second ferromagnetic metal layer is larger than thespin resistance of the iron (Fe) or iron-based alloy. By using such astructure, backflow of the spin current from the second ferromagneticmetal layer back into the spin-orbit torque wiring can be reduced.

In the spin current magnetization rotational element of the presentdisclosure, from the viewpoint of reducing backflow of the spin currentfrom the second ferromagnetic metal layer into the spin-orbit torquewiring, the spin resistivity of the material that constitutes at leastthe connection portion of the spin-orbit torque wiring layer that isconnected to the second ferromagnetic metal layer is preferably as largeas possible.

Materials having a large effect in reducing backflow of the spin currentfrom the second ferromagnetic metal layer into the spin-orbit torquewiring should be determined not only on the basis of the spin diffusionlength, but also with due consideration of the product of the spindiffusion length and the electrical resistivity.

Table 1 shows the electrical resistivity, the spin diffusion length, andthe spin resistivity obtained by multiplying these two values, for aplurality of non-magnetic materials known as pure spin currentgeneration materials, and for the ferromagnetic material iron (Fe). Feis a typical ferromagnetic material used as a material for theferromagnetic metal layer in a magnetoresistance effect element.

The electrical resistivity and the spin diffusion length of thenon-magnetic materials were calculated using the methods describedbelow, whereas the various parameters for Fe are values based onNon-Patent Document 4.

TABLE 1 Spin diffusion Spin Resistivity length @ RT resistivity Material[Ωμm] [μm] [Ωμm²] Ferromagnetic Fe 0.04 0.0085 3.40E−04 Non-magnetic Pt0.0981 0.0012 1.18E−04 Pd 0.1 0.0032 3.20E−04 Mo 0.05 0.035 1.75E−03 Nb0.152 0.0059 8.97E−04 W 0.049 0.036 1.76E−03 Mo_(0.99)Fe_(0.01) 0.050.03 1.50E−03

Of the non-magnetic materials shown in Table 1, it is evident thattungsten (W), molybdenum (Mo), niobium (Nb), and the alloy of Mo and Fehave larger spin resistivity values than the spin resistivity of Fe, andfrom the viewpoint of reducing the backflow of spin current from thesecond ferromagnetic metal layer back into the spin-orbit torque wiring,are therefore preferable as the material that constitutes at least theconnection portion of the spin-orbit torque wiring layer that isconnected to the second ferromagnetic metal layer.

(Spin Diffusion Length)

The spin current depends on the ratio between the distance d and thespin diffusion length λ, and reduces exponentially in accordance withexp(−d/λ). The spin diffusion length λ is a constant that is specific tothe material, and is the distance at which the size of the spin currentreaches 1/e.

The spin diffusion length of a material can be estimated using variousmethods. Examples of known methods include non-local methods, methodsthat utilize the spin pumping effect, and methods that utilize the Hanleeffect.

The spin diffusion lengths of the non-magnetic materials shown in Table1 were obtained by non-local spin valve measurements at roomtemperature. Details of the measurement method are described below.

In a non-local measurement using a lateral spin valve structure (wherethe interface between the ferromagnetic material and the non-magneticmaterial is not a tunnel junction), solving the diffusion equationreveals that the size ΔV of the spin output (the non-local spin valvesignal) is represented by formula (2) shown below (Non-Patent Document3).

$\begin{matrix}\left\lbrack {{Numerical}\mspace{14mu} {formula}\mspace{14mu} 2} \right\rbrack & \; \\{{\Delta \; V} = {\frac{\alpha_{F}^{2}Q^{2}\mspace{11mu} R_{SN}}{{2e^{\frac{d}{\lambda_{N}}}\; Q\mspace{11mu} \left( {2 + Q} \right)} + {4\mspace{11mu} \sin \; {h\left( {d/\lambda_{N}} \right)}}}.}} & (2)\end{matrix}$

In the formula, Q is defined as Q=R_(SF)/R_(SN), wherein R_(SN) andR_(SF) represent the spin resistance values of the non-magnetic materialand the ferromagnetic material respectively, defined asR_(SN)=λ_(N)/(A_(N)σ_(N)) and R_(SF)=λ_(F)/{(1−σ_(F) ²)(A_(F)σ_(F))},

λ_(N) and λ_(F) represent the spin diffusion lengths of the non-magneticmaterial and the ferromagnetic material respectively,

A_(N) and A_(F) represent the cross-sectional areas of the regionsthrough which the spin current flows in the non-magnetic material andthe ferromagnetic material respectively,

σ_(N) and σ_(F) represent the electrical resistivity values of thenon-magnetic material and the ferromagnetic material respectively,

α_(F) represents the spin polarization of the ferromagnetic material,and

d represents the distance between the two ferromagnetic fine wires.

As illustrated in FIG. 3, a lateral spin valve structure has a structurein which two ferromagnetic fine wires 12 and 13 disposed with aseparation therebetween are linked by a single non-magnetic fine wire14.

A direct electric current is applied between one ferromagnetic fine wire12 and a reference electrode 15, and the voltage is measured between theother ferromagnetic fine wire 13 and a reference electrode 16. At thispoint, a magnetic field is applied, and the magnetizations of the twoferromagnetic fine wires are reversed. Because the shapes (sizes) of theelements differ, a shape anisotropy effect causes variation in thereversed magnetic field, and therefore depending on the region of themagnetic field, the magnetization orientation of the ferromagnetic finewires can be formed in parallel or in antiparallel. The spin outputresistance can be determined from the difference in voltage between theparallel case and the antiparallel case.

Measurements were performed for at least five values for theferromagnetic fine wire separation distance d within a range from 7 nmto 1 μm. In order to improve the accuracy, it is necessary to determinethe number of ferromagnetic fine wire separation distance values d inaccordance with the size of the spin diffusion length. In a non-localmeasurement, if the ferromagnetic fine wire separation distance d is toosmall, then the amount of noise increases, and therefore the distancecannot be made too small. Accordingly, when the spin diffusion length issmall, measurement tends to be performed at the tail of the exponentialfunction, but if the number of measurement points, namely the number offerromagnetic fine wire separation distance values d, is increased, themeasurement accuracy can be improved.

By plotting the ferromagnetic fine wire separation distance along thehorizontal axis and the spin output ΔV along the vertical axis, and thenperforming fitting using the formula (2), the spin diffusion length ofeach of the non-magnetic materials was determined.

In the case of the Mo, W and MoFe alloy in Table 1, the ferromagneticfine wire separation distance d was increased in 5 nm intervals from 25nm, and 5 measurements were performed. Further, in the case of Nb, theferromagnetic fine wire separation distance d was increased in 1 nmintervals from 7 nm, and 20 measurements were performed. Further, in thecase of Pd, the ferromagnetic fine wire separation distance d wasincreased in 1 nm intervals from 7 nm, and 40 measurements wereperformed. Furthermore, in the case of Pt, the ferromagnetic fine wireseparation distance d was increased in 1 nm intervals from 7 nm, and 100measurements were performed. Limitations of the production apparatusmean that resolutions better than 7 nm could not be achieved. The abovechanges in the ferromagnetic fine wire separation distance d representdesign values. However, by measuring a suitably large number ofmeasurement points, any error between the design values and the actualvalues can be statistically compensated.

In the case of materials such as Pt and Pd, for which the spin diffusionlength is short, measurement can usually be performed by a method thatutilizes the spin pumping effect or a method that utilizes the Hanleeffect.

In the measurements described above, a structure not having a tunnelinsulating film at the interface between the ferromagnetic material andthe non-magnetic material was used, but a structure having a tunnelinsulating film may also be used. For example, by using a film formedfrom MgO as a tunnel insulating film, a larger output ΔV can be obtainedas a result of coherent tunnelling.

(Electrical Resistivity)

As illustrated in FIG. 4, the electrical resistivity was measured usinga typical four-terminal method. A direct electric current was appliedbetween the reference electrodes, and the reduction in the voltagebetween the ferromagnetic fine wires was measured. Further, in order toavoid element fluctuations and errors, the electrical resistivity of thenon-magnetic fine wire was determined from a plurality of results forelements having different separation distances between the ferromagneticfine wires. Specifically, the separation distance between theferromagnetic fine wires was plotted along the horizontal axis and theelectrical resistance was plotted along the vertical axis, and theelectrical resistivity was determined from the slope of the plot.

In the case of the Mo and W in Table 1, measurements were performed forfive values for the ferromagnetic fine wire separation distance d. Inthe case of Nb, measurements were performed for 20 values for theferromagnetic fine wire separation distance d. Further, in the case ofPd, measurements were performed for 40 values for the ferromagnetic finewire separation distance d. Furthermore, in the case of Pt, measurementswere performed for 100 values for the ferromagnetic fine wire separationdistance d.

Materials that can be used for forming the spin-orbit torque wiring aredescribed below, under the premise that the spin resistance of at leastthe connection portion of the spin-orbit torque wiring layer that isconnected to the second ferromagnetic metal layer is larger than thespin resistance of the second ferromagnetic metal layer.

The spin-orbit torque wiring may contain a non-magnetic heavy metal.Here, the term “heavy metal” is used to mean a metal having a specificgravity at least as large as that of yttrium. The spin-orbit torquewiring may also be formed solely from a non-magnetic heavy metal.

In such a case, the non-magnetic heavy metal is preferably anon-magnetic metal with a large atomic number of 39 or greater havingd-electrons or f-electrons in the outermost shell. The reason for thispreference is that such non-magnetic metals exhibit large spin-orbitinteractions that generate a spin Hall effect. The spin-orbit torquewiring 2 may also be formed solely from a non-magnetic metal with alarge atomic number of 39 or greater and having d-electrons orf-electrons in the outermost shell.

Typically, when an electric current is passed through a metal, all ofthe electrons move in the opposite direction from the current regardlessof spin orientation, but in the case of a non-magnetic metal with alarge atomic number having d-electrons or f-electrons in the outermostshell, because the spin-orbit interactions are large, the spin Halleffect means that the direction of electron movement is dependent on theelectron spin orientation, meaning a pure spin current J_(S) developsmore readily.

Furthermore, the spin-orbit torque wiring may contain a magnetic metal.The term “magnetic metal” means a ferromagnetic metal or anantiferromagnetic metal. By including a trace amount of a magnetic metalin the non-magnetic metal, the spin-orbit interactions can be amplified,thereby increasing the spin current generation efficiency of theelectric current passed through the spin-orbit torque wiring. Thespin-orbit torque wiring may also be formed solely from anantiferromagnetic metal.

Because spin-orbit interactions occur within interior locations peculiarto the substance of the spin-orbit torque wiring material, pure spincurrents also develop in non-magnetic materials. If a trace amount of amagnetic metal is added to the spin-orbit torque wiring material, thenbecause the magnetic metal itself scatters the flowing electron spin,the efficiency of spin current generation is enhanced. However, if theamount added of the magnetic metal is too large, then the generated purespin current tends to be scattered by the added magnetic metal,resulting in a strengthening of the action reducing the spin current.Accordingly, it is preferable that the molar fraction of the addedmagnetic metal is considerably lower than the molar fraction of the maincomponent of the pure spin current generation portion in the spin-orbittorque wiring. As a guide, the molar fraction of the added magneticmetal is preferably not more than 3%.

Furthermore, the spin-orbit torque wiring may contain a topologicalinsulator. The spin-orbit torque wiring may also be formed solely from atopological insulator. A topological insulator is a substance in whichthe interior of the substance is an insulator or high-resistance body,but the surface of the substance forms a metal-like state with spinpolarization. Some substances have a type of internal magnetic fieldknown as a spin-orbit interaction. Accordingly, even if an externalmagnetic field does not exist, the effect of these spin-orbitinteractions generates a new topological phase. This is a topologicalinsulator, which as a result of strong spin-orbit interactions and thebreak of inversion symmetry at the edges, is able to generate a purespin current with good efficiency.

Examples of preferred topological insulators include SnTe,Bi_(1.5)Sb_(0.5)Te_(1.7)Se_(1.3), TlBiSe₂, Bi₂Te₃ and(Bi_(1-x)Sb_(x))₂Te₃. These topological insulators can generate spincurrent with good efficiency.

The following description includes mainly examples in which the spincurrent magnetization rotational element of the present disclosure isapplied to magnetoresistance effect elements. However, applications ofthe spin current magnetization rotational element are not limited tomagnetoresistance effect elements, and the spin current magnetizationrotational element can also be used in other applications. For example,the spin current magnetization rotational element can also be used in aspatial light modulator, by installing a spin current magnetizationrotational element in each pixel and using the magneto-optical effect tospatially modulate the incident light, or alternatively, in order toavoid the hysteresis effect caused by the coercive force of the magnetin a magnetic sensor, the magnetic field applied to the easy axis ofmagnetization of the magnet can be replaced with a spin currentmagnetization rotational element.

(Magnetoresistance Effect Element)

FIG. 5 represents an example of an application of the spin currentmagnetization rotational element of the present disclosure, and is aperspective view schematically illustrating a magnetoresistance effectelement according to one embodiment of the present disclosure.

A magnetoresistance effect element 100 according to one embodiment ofthe present disclosure has a magnetoresistance effect element portion20, and spin-orbit torque wiring 40 which extends in a direction thatintersects the stacking direction of the magnetoresistance effectelement portion 20, and is connected to the magnetoresistance effectelement portion 20 (a second ferromagnetic metal layer 23), wherein thespin resistance of at least the connection portion of the spin-orbittorque wiring layer that is connected to the second ferromagnetic metallayer is larger than the spin resistance of the second ferromagneticmetal layer. This magnetoresistance effect element 100 according to oneembodiment of the present disclosure can also be described as having thespin current magnetization rotational element 101 of the presentdisclosure, a first ferromagnetic metal layer 21 having a fixedmagnetization orientation, and a non-magnetic layer 22.

In the following description, and in FIG. 5, the case in which thespin-orbit torque wiring extends in a direction orthogonal to thestacking direction of the magnetoresistance effect element is describedas one example of the structure in which the spin-orbit torque wiringextends in a direction that intersects the stacking direction of themagnetoresistance effect element.

In FIG. 5, wiring 30 for supplying an electric current in the stackingdirection of the magnetoresistance effect element portion 20, asubstrate 10 for forming that wiring 30, and a cap layer 24 are alsoshown.

In the following description, the stacking direction of themagnetoresistance effect element portion 20 is deemed the z-direction,the direction perpendicular to the z-direction and parallel with thespin-orbit torque wiring 40 is deemed the x-direction, and the directionorthogonal to the x-direction and the z-direction is deemed they-direction.

In the example illustrated in FIG. 5, the spin-orbit torque wiring 40 isformed on top of the second ferromagnetic metal layer 23, but may alsobe formed in the reverse order.

<Magnetoresistance Effect Element Portion>

The magnetoresistance effect element portion 20 has the firstferromagnetic metal layer 21 having a fixed magnetization orientation,the second ferromagnetic metal layer 23 having a variable magnetizationorientation, and the non-magnetic layer 22 sandwiched between the firstferromagnetic metal layer 21 and the second ferromagnetic metal layer23.

The magnetoresistance effect element portion 20 functions by having themagnetization of the first ferromagnetic metal layer 21 fixed in asingle direction, while the orientation of the magnetization of thesecond ferromagnetic metal layer 23 is able to vary relatively. Whenapplied to coercive force difference (pseudo spin valve) MRAM, thecoercive force of the first ferromagnetic metal layer is larger than thecoercive force of the second ferromagnetic metal layer, whereas whenapplied to exchange bias (spin valve) MRAM, the magnetizationorientation of the first ferromagnetic metal layer is fixed by exchangecoupling with an antiferromagnetic layer.

Further, when the non-magnetic layer 22 is formed from an insulator, themagnetoresistance effect element portion 20 is a tunnelingmagnetoresistance (TMR) element, whereas when the non-magnetic layer 22is formed from a metal, the magnetoresistance effect element portion 20is a giant magnetoresistance (GMR) element.

A conventional magnetoresistance effect element portion structure can beused for the magnetoresistance effect element portion included in thepresent disclosure. For example, each layer may be composed of aplurality of layers, and the structure may also include other layerssuch as an antiferromagnetic layer for fixing the magnetizationorientation of the first ferromagnetic metal layer.

The first ferromagnetic metal layer 21 is also called the fixed layer orreference layer, whereas the second ferromagnetic metal layer 23 is alsocalled the free layer or the memory layer.

The first ferromagnetic metal layer 21 and the second ferromagneticmetal layer 23 may be either in-plane magnetization films in which themagnetization direction is parallel with the in-plane direction, orperpendicular magnetization films in which the magnetization directionis in a direction perpendicular to the layer.

Conventional materials can be used as the material for the firstferromagnetic metal layer 21. For example, metals selected from thegroup consisting of Cr, Mn, Co, Fe and Ni, and alloys containing atleast one of these metals and having ferromagnetism can be used.Further, alloys containing at least one of these metals and at least oneelement among B, C and N can also be used. Specific examples includeCo—Fe and Co—Fe—B.

Further, in order to achieve higher output, a Heusler alloy such asCo₂FeSi is preferably used. Heusler alloys contain intermetalliccompounds having a chemical composition of X₂YZ, wherein X is a noblemetal element or a transition metal element belonging to the Co, Fe, Nior Cu group of the periodic table, Y is a transition metal belonging tothe Mn, V, Cr or Ti group of the periodic table, and the elementalspecies of X can be used as Y, and Z is a typical element of group IIIto group V. Specific examples include Co₂FeSi, Co₂MnSi, andCo₂Mn_(1-a)Fe_(a)Al_(b)Si_(1-b).

Furthermore, in order to increase the coercive force of the firstferromagnetic metal layer 21 relative to the second ferromagnetic metallayer 23, an antiferromagnetic material such as IrMn or PtMn may be usedas the material that contacts the first ferromagnetic metal layer 21.Moreover, in order to ensure that the leakage magnetic field of thefirst ferromagnetic metal layer 21 does not affect the secondferromagnetic metal layer 23, a structure having synthetic ferromagneticcoupling may be used.

Furthermore, in those cases where the orientation of the magnetizationof the first ferromagnetic metal layer 21 is perpendicular to thestacking surface, a stacked film of Co and Pt is preferably used.Specifically, the structure of the first ferromagnetic metal layer 21may be [Co (0.24 nm)/Pt (0.16 nm)]₆/Ru (0.9 nm)/[Pt (0.16 nm)/Co (0.16nm)]₄/Ta (0.2 nm)/FeB (1.0 nm).

Conventional materials can be used for the non-magnetic layer 22.

For example, when the non-magnetic layer 22 is formed from an insulator(and forms a tunnel barrier layer), examples of materials that can beused include Al₂O₃, SiO₂, MgO and MgAl₂O₄. In addition to thesematerials, materials in which a portion of the Al, Si or Mg has beensubstituted with Zn or Be or the like can also be used. Among the abovematerials, MgO and MgAl₂O₄ are materials that enable the realization ofcoherent tunneling, and therefore enable efficient injection of spin.

Further, when the non-magnetic layer 22 is formed from a metal, examplesof materials that can be used include Cu, Au, and Ag and the like.

Furthermore, as illustrated in FIG. 5, a cap layer 24 is preferablyformed on the surface of the second ferromagnetic metal layer 23 on theopposite side to the non-magnetic layer 22. The cap layer 24 cansuppress the diffusion of elements from the second ferromagnetic metallayer 23. Further, the cap layer 24 also contributes to the crystalorientation of each of the layers of the magnetoresistance effectelement portion 20. As a result, by providing the cap layer 24, themagnetism of the first ferromagnetic metal layer 21 and the secondferromagnetic metal layer 23 of the magnetoresistance effect elementportion 20 can be stabilized, and the resistance of themagnetoresistance effect element portion 20 can be lowered.

A material having high conductivity is preferably used for the cap layer24. Examples of materials that may be used include Ru, Ta, Cu, Ag andAu. The crystal structure of the cap layer 24 is preferably selectedappropriately from among an fcc structure, an hcp structure and a bccstructure, in accordance with the crystal structure of the adjacentferromagnetic metal layer.

Further, the use of at least one metal selected from the groupconsisting of silver, copper, magnesium and aluminum for the cap layer24 is preferred. Details are provided below, but in those cases wherethe spin-orbit torque wiring 40 and the magnetoresistance effect elementportion 20 are connected via the cap layer 24, it is preferable that thecap layer 24 does not dissipate the spin propagated from the spin-orbittorque wiring 40. Silver, copper, magnesium, and aluminum and the likehave a long spin diffusion length of at least 100 nm, and are known tobe resistant to spin dissipation.

The thickness of the cap layer 24 is preferably not more than the spindiffusion length of the material that constitutes the cap layer 24.Provided the thickness of the cap layer 24 is not more than the spindiffusion length, the spin propagated from the spin-orbit torque wiring40 can be transmitted satisfactorily to the magnetoresistance effectelement portion 20.

<Substrate>

The substrate 10 preferably has superior smoothness. Examples ofmaterials that can be used to obtain a surface having superiorsmoothness include Si and AlTiC and the like.

A base layer (not shown in the figure) may be formed on the surface ofthe substrate 10 on the side facing the magnetoresistance effect elementportion 20. By providing a base layer, the crystallinity such as thecrystal orientation and crystal grain size of each of the layers,including the first ferromagnetic metal layer 21, stacked on top of thesubstrate 10 can be controlled.

The base layer preferably has insulating properties. This is to preventdissipation of the electric current flowing through the wiring 30 andthe like. Various materials can be used for the base layer.

In one example, a nitride layer having a (001)-oriented NaCl structureand containing at least one element selected from the group consistingof Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al and Ce can be used for the baselayer.

In another example, a (002)-oriented perovskite-based conductive oxidelayer represented by a compositional formula of XYO₃ can be used as thebase layer. In this formula, site X includes at least one elementselected from the group consisting of Sr, Ce, Dy, La, K, Ca, Na, Pb andBa, and the site Y includes at least one element selected from the groupconsisting of Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce andPb.

In yet another example, an oxide layer having a (001)-oriented NaClstructure and containing at least one element selected from the groupconsisting of Mg, Al and Ce can be used for the base layer.

In yet another example, a layer having a (001)-oriented tetragonalstructure or cubic structure and containing at least one elementselected from the group consisting of Al, Cr, Fe, Co, Rh, Pd, Ag, Ir,Pt, Au, Mo and W can be used for the base layer.

Further, the base layer is not limited to a single layer, and aplurality of the layers described in the above examples may be stacked.By appropriate modification of the structure of the base layer, thecrystallinity of each layer of the magnetoresistance effect elementportion 20 can be enhanced, and the magnetic characteristics can beimproved.

<Wiring>

The wiring 30 is connected electrically to the first ferromagnetic metallayer 21 of the magnetoresistance effect element portion 20, and in FIG.5, the wiring 30, the spin-orbit torque wiring 40 and a power supply(not shown in the figure) form a closed circuit, enabling an electriccurrent to flow through the stacking direction of the magnetoresistanceeffect element portion 20.

There are no particular limitations on the material for the wiring 30,provided it is a material having high conductivity. For example,aluminum, silver, copper, or gold or the like can be used.

In the following description, the types of structures that can beadopted by the spin-orbit torque wiring are described with reference toFIG. 6 to FIG. 9, under the premise that the spin resistance of at leastthe connection portion of the spin-orbit torque wiring layer that isconnected to the second ferromagnetic metal layer is larger than thespin resistance of the second ferromagnetic metal layer.

FIG. 6 to FIG. 9 are schematic views for describing embodiments of thespin-orbit torque wiring, and in each figure, (a) is a cross-sectionalview, and (b) is a plan view.

In the magnetoresistance effect element of the present disclosure,regardless of whether the structure uses only SOT generated by pure spincurrent to perform magnetization rotation of the magnetoresistanceeffect element (also referred to as an “SOT only” structure), or whetherthe structure uses SOT generated by pure spin current in combinationwith STT in a conventional magnetoresistance effect element that usesSTT (also referred to as an “STT and SOT combination” structure),because the electric current passed through the spin-orbit torque wiringis a typical current that is accompanied by an electric charge flow, thecurrent flow generates Joule heat.

The embodiments of the spin-orbit torque wiring illustrated in FIG. 6 toFIG. 9 are examples of structures for reducing the Joule heat generatedby the electric current passed through the spin-orbit torque wiring byusing structures other than the materials described above.

In an “STT and SOT combination” structure, the electric current used forcausing magnetization rotation of the magnetoresistance effect elementportion of the present disclosure includes not only the electric currentpassed directly into the magnetoresistance effect element portion inorder to utilize the STT effect (hereafter also referred to as the “STTreversal current”), but also the electric current passed through thespin-orbit torque wiring in order to utilize the SOT effect (hereafteralso referred to as the “SOT reversal current”). Because each of theseelectric currents is a typical current accompanied by an electric chargeflow, the flow of these electric currents generates Joule heat.

In this structure, because a combination of magnetization rotation dueto the STT effect and magnetization rotation due to the SOT effect isused, the STT reversal current is reduced compared with a structure inwhich magnetization rotation is performed using only the STT effect, butthe energy associated with the SOT reversal current is consumed.

The heavy metal, which is a material that readily generates a pure spincurrent, has a higher electric resistivity than the types of metalstypically used as wiring.

As a result, from the viewpoint of reducing the Joule heat generated bythe SOT reversal current, it is preferable that rather than having theentire spin-orbit torque wiring formed solely from a material that cangenerate a pure spin current, the spin-orbit torque wiring preferablyhas a portion having low electric resistivity. In other words, from theabove viewpoint, the spin-orbit torque wiring is preferably composed ofa portion formed from a material that generates a pure spin current (aspin current generation portion), and a conductive portion having asmall electrical resistivity. The conductive portion is preferablyformed from a material having a smaller electrical resistivity than thespin current generation portion.

The spin current generation portion may be formed from any materialcapable of generating a pure spin current, and may, for example, have astructure composed of portions of a plurality of different materials.

For the conductive portion, the types of materials typically used aswiring can be used. For example, aluminum, silver, copper, or gold orthe like can be used. The conductive portion may be formed from anymaterial having a smaller electrical resistivity than the spin currentgeneration portion, and may have a structure composed of portions of aplurality of different materials.

A pure spin current may also be generated in the conductive portion. Inthis case, in order to distinguish between the spin current generationportion and the conductive portion, those portions formed from materialslisted in the present description as materials for use as the spincurrent generation portion or the conductive portion can bedifferentiated as the spin current generation portion or the conductiveportion respectively. Furthermore, portions besides the main portionthat generates the pure spin current, which have a smaller electricalresistivity than the main portion, can be differentiated from the spincurrent generation portion as conductive portions.

The spin current generation portion may contain a non-magnetic heavymetal. In this case, any heavy metal capable of generating a pure spincurrent may be included. Further, in this case, it is preferable eitherthat the heavy metal capable of generating a pure spin current has amuch lower concentration range than the main component of the spincurrent generation portion, or that the heavy metal capable ofgenerating a pure spin current is the main component, and represents,for example, 90% or more of the spin current generation portion. In thiscase, the heavy metal capable of generating a pure spin current ispreferably composed 100% of a non-magnetic metal with an atomic numberof 39 or greater having d-electrons or f-electrons in the outermostshell.

Here, the expression that “the heavy metal capable of generating a purespin current has a much lower concentration range than the maincomponent of the spin current generation portion” means that, forexample, in a spin current generation portion containing copper as themain component, the concentration of the heavy metal represents a molarfraction of 10% or less. In those cases where the main componentconstituting the spin current generation portion is composed of a metalother than the aforementioned heavy metal, the concentration of theheavy metal within the spin current generation portion is preferably amolar fraction of not more than 50%, and more preferably a molarfraction of 10% or less. These concentration ranges represent rangesthat enable the electron spin scattering effect to be obtainedeffectively. When the concentration of heavy metal is low, a light metalhaving a smaller atomic number than the heavy metal becomes the maincomponent. In this case, the heavy metal does not form an alloy with thelight metal, but rather, it is assumed that atoms of the heavy metal aredispersed in a disorderly manner within the light metal. Becausespin-orbit interactions in the light metal are weak, pure spin currentis unlikely to be generated by the spin Hall effect. However, whenelectrons pass the heavy metal within the light metal, a spin scatteringeffect occurs at the interface between the light metal and the heavymetal, and therefore even when the concentration of the heavy metal islow, a pure spin current can be generated with good efficiency. When theconcentration of the heavy metal exceeds 50%, although the proportion ofspin Hall effect within the heavy metal increases, the effect at theinterface between the light metal and the heavy metal decreases,resulting in a reduction on the overall effect. Accordingly, a heavymetal concentration at which a satisfactory interface effect can beanticipated is preferable.

Further, in those cases where the spin-orbit torque wiring contains amagnetic metal, the spin current generation portion in the spin-orbittorque wiring may be composed of an antiferromagnetic metal. Anantiferromagnetic metal can produce a similar effect to the case wherethe heavy metal is composed 100% of a non-magnetic metal with an atomicnumber of 39 or greater having d-electrons or f-electrons in theoutermost shell. The antiferromagnetic metal is, for example, preferablyIrMn or PtMn or the like, and the thermally stable IrMn is particularlypreferred.

Further, in those cases where the spin-orbit torque wiring contains atopological insulator, the spin current generation portion in thespin-orbit torque wiring may be composed of the topological insulator.The topological insulator is, for example, SnTe,Bi_(1.5)Sb_(0.5)Te_(1.7)Se_(1.3), TlBiSe₂, Bi₂Te₃, or(Bi_(1-x)Sb_(x))₂Te₃ or the like. These topological insulators arecapable of generating a spin current with high efficiency.

In order to ensure that the pure spin current generated in thespin-orbit torque wiring diffuses effectively into the magnetoresistanceeffect element portion, at least a portion of the spin currentgeneration portion must be connected to the second ferromagnetic metallayer. When a cap layer exists, at least a portion of the spin currentgeneration portion must be connected to the cap layer.

In the magnetoresistance effect element of the present disclosure, thespin-orbit torque wiring layer must have a connection portion that isconnected to the second ferromagnetic metal layer, but the connectionportion that is connected to the second ferromagnetic metal layer may beat least a portion of the spin current generation portion.

The embodiments of spin-orbit torque wiring illustrated in FIG. 6 toFIG. 9 are all structures in which at least a portion of the spincurrent generation portion is connected to the second ferromagneticmetal layer.

In the embodiment illustrated in FIG. 6, a connection surface 40′ wherethe spin-orbit torque wiring 40 contacts the second ferromagnetic metallayer 23 is formed entirely from a spin current generation portion 41,and the spin current generation portion 41 is sandwiched betweenconductive portions 42A and 42B.

The connection portion 40B of the spin-orbit torque wiring 40 that isconnected to the second ferromagnetic metal layer 23 is the portionshown by a two-dot chain line in FIG. 6(a), and indicates the portion(including the portion in the thickness direction) of the spin-orbittorque wiring that overlaps with the second ferromagnetic metal layerwhen viewed in plan view from the stacking direction. In other words,the enclosed portion obtained by offsetting a portion of the secondferromagnetic metal layer 23, shown as a plan view projection by thedashed line in FIG. 6(b), from one surface 40 a (see FIG. 6(a)) throughthe thickness direction to the opposing surface 40 b (see FIG. 6(a)),represents the connection portion of the spin-orbit torque wiring. Theconnection portion 40B where the spin-orbit torque wiring 40 shown inFIG. 6 is connected to the second ferromagnetic metal layer 23 is formedentirely from the spin current generation portion 41. In other words,the connection portion 40B is a portion of the spin current generationportion 41.

The connection between the spin-orbit torque wiring and the secondferromagnetic metal layer may be a “direct” connection, or may involveconnection “via another layer” such as the cap layer described below,and there are no restrictions on the way in which the spin-orbit torquewiring and the second ferromagnetic metal layer are connected (joined orbonded), provided the pure spin current generated in the spin-orbittorque wiring can flow into the second ferromagnetic metal layer.

In those cases where the spin current generation portion and theconductive portion are disposed electrically in parallel, the electriccurrent flowing through the spin-orbit torque wiring will flow throughthe spin current generation portion and the conductive portion inproportions inversely proportional to the sizes of the resistance of thespin current generation portion and the conductive portion.

From the viewpoint of the efficiency of the pure spin current generationrelative to the SOT reversal current, in order to ensure that all of theelectric current flowing through the spin-orbit torque wiring flowsthrough the spin current generation portion, there must be no portionswhere the spin current generation portion and the conductive portion aredisposed electrically in parallel, and the two portions must be disposedentirely in series.

The spin-orbit torque wirings illustrated in FIG. 6 to FIG. 9 areillustrated in plan view from the stacking direction of themagnetoresistance effect element, and represent structures in whichthere are no portions where the spin current generation portion and theconductive portion are disposed electrically in parallel, and in whichthe efficiency of the pure spin current generation relative to the SOTreversal current is highest in the structure having the cross-sectionillustrated in (a) in FIGS. 6, 7, and 9.

The spin-orbit torque wiring 40 illustrated in FIG. 6 has a structure inwhich the spin current generation portion 41 is superimposed so as tocover all of a connection portion 23′ of the second ferromagnetic metallayer 23 when viewed in plan view from the stacking direction of themagnetoresistance effect element portion 20, and the thickness directionof the spin-orbit torque wiring 40 is composed solely of the spincurrent generation portion 41, with the conductive portions 42A and 42Bpositioned so as to sandwich the spin current generation portion 41 inthe direction of the electric current flow. In a modification of thespin-orbit torque wiring illustrated in FIG. 6, the spin currentgeneration portion may be superimposed so as to overlap the connectionportion of the second ferromagnetic metal layer when viewed in plan viewfrom the stacking direction of the magnetoresistance effect element,with the remaining structure the same as the spin-orbit torque wiringillustrated in FIG. 6.

The spin-orbit torque wiring 40 illustrated in FIG. 7 has a structure inwhich the spin current generation portion 41 is superimposed on aportion of the connection portion 23′ of the second ferromagnetic metallayer 23 when viewed in plan view from the stacking direction of themagnetoresistance effect element portion 20, and the thickness directionof the spin-orbit torque wiring 40 is composed solely of the spincurrent generation portion 41, with the conductive portions 42A and 42Bpositioned so as to sandwich the spin current generation portion 41 inthe direction of the electric current flow.

A connection portion 40BB of the spin-orbit torque wiring 40 that isconnected to the second ferromagnetic metal layer 23 is the portionshown by a two-dot chain line in FIG. 7(a), and indicates the portion(including the portion in the thickness direction) of the spin-orbittorque wiring that overlaps with the second ferromagnetic metal layerwhen viewed in plan view from the stacking direction. The connectionportion 40BB where the spin-orbit torque wiring 40 shown in FIG. 7 isconnected to the second ferromagnetic metal layer 23 is formed from theentire spin current generation portion 41 and portions of the conductiveportions 42A and 42B.

The spin-orbit torque wiring 40 illustrated in FIG. 8 has a structure inwhich the spin current generation portion 41 is superimposed so as tocover all of the connection portion 23′ of the second ferromagneticmetal layer 23 when viewed in plan view from the stacking direction ofthe magnetoresistance effect element portion 20, but in which thethickness direction of the spin-orbit torque wiring 40 includes the spincurrent generation portion 41 and a conductive portion 42C stacked inthat order from the side of the second ferromagnetic metal layer, withthe conductive portions 42A and 42B positioned so as to sandwich, in thedirection of the electric current flow, the portion where the spincurrent generation portion 41 and the conductive portion 42C arestacked. In a modification of the spin-orbit torque wiring illustratedin FIG. 8, the spin current generation portion may be superimposed so asto overlap the connection portion of the second ferromagnetic metallayer when viewed in plan view from the stacking direction of themagnetoresistance effect element, with the remaining structure the sameas the spin-orbit torque wiring illustrated in FIG. 8.

A connection portion 40BBB of the spin-orbit torque wiring 40 that isconnected to the second ferromagnetic metal layer 23 is the portionshown by a two-dot chain line in FIG. 8(a), and indicates the portion(including the portion in the thickness direction) of the spin-orbittorque wiring that overlaps with the second ferromagnetic metal layerwhen viewed in plan view from the stacking direction. The connectionportion 40BBB where the spin-orbit torque wiring 40 shown in FIG. 8 isconnected to the second ferromagnetic metal layer 23 is formed entirelyfrom the spin current generation portion 41. In other words, theconnection portion 40BBB is a portion of the spin current generationportion 41.

The spin-orbit torque wiring 40 illustrated in FIG. 9 has a structurecomposed of a first spin current generation portion 41A in which thespin current generation portion 41 is formed along the entire surface onthe side facing the second ferromagnetic metal layer, a second spincurrent generation portion 41B, which is stacked on top of the firstspin current generation portion and superimposed so as to cover all ofthe connection portion 23′ of the second ferromagnetic metal layer 23when viewed in plan view from the stacking direction of themagnetoresistance effect element portion 20, and in which the thicknessdirection of the spin-orbit torque wiring 40 is composed solely of thespin current generation portion, and conductive portions 42A and 42Bwhich are positioned so as to sandwich the second spin currentgeneration portion 41B in the direction of the electric current flow. Ina modification of the spin-orbit torque wiring illustrated in FIG. 9,the second spin current generation portion may be superimposed so as tooverlap the connection portion of the second ferromagnetic metal layerwhen viewed in plan view from the stacking direction of themagnetoresistance effect element, with the remaining structure the sameas the spin-orbit torque wiring illustrated in FIG. 9.

In the structure illustrated in FIG. 9, because the area of contactbetween the spin current generation portion 41 and the conductiveportion 42 is large, the adhesion between the non-magnetic metal havinga high atomic number that constitutes the spin current generationportion 41 and the metal that constitutes the conductive portion 42 issuperior.

A connection portion 40BBBB of the spin-orbit torque wiring 40 that isconnected to the second ferromagnetic metal layer 23 is the portionshown by a two-dot chain line in FIG. 9(a), and indicates the portion(including the portion in the thickness direction) of the spin-orbittorque wiring that overlaps with the second ferromagnetic metal layerwhen viewed in plan view from the stacking direction. The connectionportion 40BBBB where the spin-orbit torque wiring 40 shown in FIG. 9 isconnected to the second ferromagnetic metal layer 23 is formed entirelyfrom the spin current generation portion 41. In other words, theconnection portion 40BBBB is a portion of the spin current generationportion 41.

The magnetoresistance effect element of the present disclosure can beproduced using conventional methods. A method for producing themagnetoresistance effect elements illustrated in FIG. 6 to FIG. 9 isdescribed below.

First, the magnetoresistance effect element portion 20 can be formed,for example, using a magnetron sputtering apparatus. In those caseswhere the magnetoresistance effect element portion 20 is a TMR element,a tunnel barrier layer is formed on the first ferromagnetic metal layerby first sputtering about 0.4 to 2.0 nm of aluminum and a metal thinfilm that can form divalent cations of a plurality of non-magneticelements, and then performing a plasma oxidation or a natural oxidationby oxygen introduction, followed by a heat treatment. Examples ofmethods that can be used as the deposition method besides magnetronsputtering, include other thin film formation methods such as vapordeposition methods, laser ablation methods and MBE methods.

Following deposition and shape formation of the magnetoresistance effectelement portion 20, the spin current generation portion 41 is preferablyformed first. This is because forming a structure that is best capableof suppressing scattering of pure spin current from the spin currentgeneration portion 41 to the magnetoresistance effect element portion 20leads to superior efficiency.

Following deposition and shape formation of the magnetoresistance effectelement portion 20, the region surrounding the processedmagnetoresistance effect element portion 20 is covered with a resist orthe like to form a surface that includes the upper surface of themagnetoresistance effect element portion 20. At this time, the uppersurface of the magnetoresistance effect element portion 20 is preferablyplanarized. By planarizing the surface, spin scattering at the interfacebetween the spin current generation portion 41 and the magnetoresistanceeffect element portion 20 can be suppressed.

Next, the material for the spin current generation portion 41 isdeposited on the planarized upper surface of the magnetoresistanceeffect element portion 20. This deposition may be performed usingsputtering or the like.

Subsequently, a resist or protective film is placed on the region inwhich the spin current generation portion 41 is to be formed, and theunneeded portions are removed using an ion milling method or reactiveion etching (RIE) method.

Next, the material that constitutes the conductive portion 42 isdeposited by sputtering or the like, and the resist or the like isremoved to complete formation of the spin-orbit torque wiring 40. Whenthe shape of the spin current generation portion 41 is complex,formation of the resist or protective film and deposition of the spincurrent generation portion 41 may be performed across a plurality ofrepetitions.

The spin-orbit torque wiring layer may have a narrow section in at leasta section of the portion that is connected to the second ferromagneticmetal layer. This narrow section is a section that has a smallercross-sectional area when cut through a section orthogonal to thedirection of extension (the lengthwise direction) of the spin-orbittorque wiring layer than the other portions of the spin-orbit torquewiring besides the narrow section. The electric current flowing throughthe spin-orbit torque wiring layer develops a higher current density inthis narrow section, resulting in a pure spin current of high densityflowing into the second ferromagnetic metal layer.

FIG. 10 is a cross-sectional view illustrating a section cut through theyz plane of a magnetoresistance effect element according to oneembodiment of the present disclosure.

The effects for the case when the magnetoresistance effect element 100is an “STT and SOT combination” structure are described below based onFIG. 10.

As illustrated in FIG. 10, there are two types of electric currents inthe magnetoresistance effect element 100. One of these is a current I₁(STT reversal current) that flows through the stacking direction of themagnetoresistance effect element portion 20, and flows though thespin-orbit torque wiring 40 and the wiring 30. In FIG. 10, the currentI₁ is deemed to flow in order through the spin-orbit torque wiring 40,the magnetoresistance effect element 20, and then the wiring 30. In thiscase, the electrons flow in order through the wiring 30, themagnetoresistance effect element 20 and then the spin-orbit torquewiring 40.

The other electric current is a current I₂ (SOT reversal current) thatflows along the direction of extension of the spin-orbit torque wiring40.

The current I₁ and the current I₂ mutually intersect (orthogonally), andin the portion where the magnetoresistance effect element 20 isconnected to the spin-orbit torque wiring 40 (reference sign 24′indicates the connection portion on the side of the magnetoresistanceeffect element 20 (the cap layer 24), and the reference sign 40′indicates the connection portion on the side of the spin-orbit torquewiring 40), the current flowing through the magnetoresistance effectelement 20 and the current flowing through the spin-orbit torque wiring40 either merge or are distributed.

By supplying the current I₁, electrons having spin oriented in the samedirection as the magnetization of the first ferromagnetic metal layer(fixed layer) 21 pass from the first ferromagnetic metal layer (fixedlayer) 21 through the non-magnetic layer 22 with the spin orientationmaintained, and these electrons act as a torque (STT) that causes theorientation of a magnetization M₂₃ of the second ferromagnetic metallayer (free layer) 23 to reverse and adopt an orientation parallel withthe orientation of the magnetization M₂₁ of the first ferromagneticmetal layer (fixed layer) 21.

On the other hand, the current I₂ corresponds with the current Iillustrated in FIG. 2. In other words, when the current I₂ flows, theupward-directed spin S⁺ and the downward-directed spin S⁻ are each benttoward the edges of the spin-orbit torque wiring 40, generating a purespin current J_(S). The pure spin current J_(S) is induced in adirection perpendicular to the direction of flow of the current I₂. Inother words, pure spin currents J_(S) are generated in the z-axisdirection and the x-axis direction in the figure. In FIG. 10, only thepure spin current is in the z-axis direction, which contributes to theorientation of the magnetization of the second ferromagnetic metal layer23, is shown.

The pure spin current J_(S) generated by supplying the current I₂ to thespin-orbit torque wiring 40 in a direction toward the front of thefigure, passes through the cap layer 24 and diffuses into the secondferromagnetic metal layer 23, with this spin affecting the magnetizationM₂₃ of the second ferromagnetic metal layer 23. In other words, in FIG.10, a spin oriented in the −x direction flows into the secondferromagnetic metal layer 23, imparting a torque (SOT) that attempts tocause a magnetization rotation of the magnetization M₂₃ of the secondferromagnetic metal layer 23 that is oriented in the +x direction.

As described above, the SOT effect due to the pure spin current isgenerated by the electric current flowing along a second current path 12is added to the STT effect generated by the electric current flowingalong a first current path I₁, causing a rotation of the magnetizationM₂₃ of the second ferromagnetic metal layer 23.

If an attempt is made to cause a magnetization rotation of themagnetization of the second ferromagnetic metal layer 23 using only theSTT effect (namely, when only the current I₁ flows), then a voltage of aprescribed voltage or greater must be applied to the magnetoresistanceeffect element 20. Although the typical drive voltage for a TMR elementis a comparatively small value of several volts or less, because thenon-magnetic layer 22 is an extremely thin film of only about severalnm, dielectric breakdown can sometimes occur. By continuing currentsupply to the non-magnetic layer 22, the weak portions of thenon-magnetic layer (portions of poor film quality or particularly thinportions) tend to be destroyed.

In contrast, in the case of the “STT and SOT combination” structure ofthe present disclosure, the magnetoresistance effect element utilizes anSOT effect in addition to the STT effect. As a result, the voltageapplied to the magnetoresistance effect element can be reduced, and thecurrent density of the electric current passed through the spin-orbittorque wiring can be reduced. By reducing the voltage applied to themagnetoresistance effect element, the lifespan of the element can belengthened. Further, by reducing the current density of the electriccurrent passed through the spin-orbit torque wiring, any dramaticreduction in the energy efficiency can be avoided.

The current density of the electric current passed through thespin-orbit torque wiring is preferably less than 1×10⁷ A/cm². If thecurrent density of the electric current passed through the spin-orbittorque wiring is too large, then the current flowing through thespin-orbit torque wiring generates heat. If heat is applied to the firstferromagnetic metal layer, then the stability of the magnetization ofthe first ferromagnetic metal layer tends to deteriorate, and unexpectedmagnetization rotations or the like can sometimes occur. If this type ofunexpected magnetization rotation occurs, then a problem can arise inwhich recorded information is rewritten. In other words, in order toavoid unexpected magnetization rotation, it is preferable that thecurrent density of the electric current flowing through the spin-orbittorque wiring is prevented from becoming too large. Provided the currentdensity of the electric current flowing through the spin-orbit torquewiring is less than 1×10⁷ A/cm², at least magnetization rotations causedby generated heat can be avoided.

FIG. 11 illustrates an example of a magnetoresistance effect elementhaving another “STT and SOT combination” structure of the presentdisclosure.

In the magnetoresistance effect element 200 illustrated in FIG. 11, thespin-orbit torque wiring 50 has an upper surface connection portion 51provided on top of the magnetoresistance effect element 20 in thestacking direction (equivalent to the spin-orbit torque wiring 40described above), and also has a side wall connection portion 52 that isconnected to the side wall of the second ferromagnetic metal layer 23.

When an electric current is passed through the spin-orbit torque wiring50, in addition to the pure spin current is generated in the uppersurface connection portion 51, a pure spin current J_(S)′ is generatedin the side wall connection portion 52.

Accordingly, not only does the pure spin current is flow from the uppersurface of the magnetoresistance effect element 20 through the cap layer24 and into the second ferromagnetic metal layer 23, but the pure spincurrent J_(S)′ flows in from the side wall of the second ferromagneticmetal layer 23, meaning the SOT effect is enhanced.

FIG. 12 illustrates a magnetoresistance effect element according to yetanother embodiment of the present disclosure.

The magnetoresistance effect element 300 illustrated in FIG. 12 hasspin-orbit torque wiring 40 on the side of the substrate 10. In thiscase, the stacking order of the first ferromagnetic metal layer 21 thatacts as the fixed layer and the second ferromagnetic metal layer 23 thatacts as the free layer is opposite that of the magnetoresistance effectelement 100 illustrated in FIG. 1.

In the magnetoresistance effect element 300 illustrated in FIG. 12, thesubstrate 10, the spin-orbit torque wiring 40, the second ferromagneticmetal layer 23, the non-magnetic layer 22, the first ferromagnetic metallayer 21, the cap layer 24 and the wiring 30 are stacked in that order.Because the second ferromagnetic metal layer 23 is stacked prior to thefirst ferromagnetic metal layer 21, the second ferromagnetic metal layer23 is less likely to be affected by lattice strain or the like than inthe magnetoresistance effect element 100. As a result, in themagnetoresistance effect element 300, the perpendicular magneticanisotropy of the second ferromagnetic metal layer 23 is enhanced.Enhancing the perpendicular magnetic anisotropy of the secondferromagnetic metal layer 23 enables the MR ratio of themagnetoresistance effect element to be improved.

FIG. 13 illustrates a configuration in which a first power supply 110for passing an electric current through the stacking direction of themagnetoresistance effect element 20 and a second power supply 120 forpassing an electric current through the spin-orbit torque wiring 40 areprovided in the magnetoresistance effect element 100 illustrated in FIG.1.

In the magnetoresistance effect element 100 of the embodiment of thepresent disclosure illustrated in FIG. 5 and FIG. 13, a so-called bottompin structure was presented as an example, in which the secondferromagnetic metal layer 23, which is stacked later in the stackingprocess and is positioned distant from the substrate 10, functions asthe free magnetization layer, and the first ferromagnetic metal layer21, which is stacked earlier in the stacking process and is positionedclose to the substrate 10, functions as the fixed magnetization layer(the pin layer), but the structure of the magnetoresistance effectelement 100 is not limited to this type of structure, and a so-calledtop pin structure may also be used.

The first power supply 110 is connected to the wiring 30 and thespin-orbit torque wiring 40. The first power supply 110 is able tocontrol the electric current that flows through the stacking directionof the magnetoresistance effect element 100.

The second power supply 120 is connected to the two ends of thespin-orbit torque wiring 40. The second power supply 120 is able tocontrol the electric current that flows through the spin-orbit torquewiring 40, which is a current that flows in a directional orthogonal tothe stacking direction of the magnetoresistance effect element 20.

As described above, the electric current flowing through the stackingdirection of the magnetoresistance effect element 20 induces STT. Incontrast, the electric current flowing through the spin-orbit torquewiring 40 induces SOT. Both the STT and the SOT contribute to themagnetization rotation of the second ferromagnetic metal layer 23.

In this manner, by using two power supplies to control the amounts ofelectric current flowing through the stacking direction of themagnetoresistance effect element 20 and the direction orthogonal to thisstacking direction, the rates of contribution of SOT and STT to themagnetization rotation can be controlled freely.

For example, in those cases where a large current cannot be passedthrough a device, the power supplies can be controlled so that STT,which has a higher energy efficiency relative to magnetization rotation,provides the main contribution. In other words, the amount of currentflowing from the first power supply 110 can be increased, while theamount of current flowing from the second power supply 120 is decreased.

Further, in those cases where a thin device is required, and thethickness of the non-magnetic layer 22 must be reduced, it is desirableto reduce the electric current flowing through the non-magnetic layer22. In such cases, the amount of current flowing from the first powersupply 110 can be reduced, and the amount of current flowing from thesecond power supply 120 can be increased, thereby increasing thecontribution rate of SOT.

Conventional power supplies can be used for the first power supply 110and the second power supply 120.

As described above, by using a magnetoresistance effect element havingthe “STT and SOT combination” structure of the present disclosure, therates of contribution of STT and SOT can be freely controlled byadjusting the amounts of electric current supplied from the first powersupply and the second power supply respectively. Accordingly, the ratesof contribution of STT and SOT can be freely controlled in accordancewith the performance required of the device, meaning the element canfunction as a more versatile magnetoresistance effect element.

(Magnetic Memory)

Magnetic memory (MRAM) of the present disclosure is provided with aplurality of magnetoresistance effect elements of the presentdisclosure.

(Magnetization Rotation Method)

A magnetization rotation method is a method of ensuring that the currentdensity flowing through the spin-orbit torque wiring in amagnetoresistance effect element of the present disclosure is less than1×10 A/cm².

If the current density of the electric current flowing through thespin-orbit torque wiring is too large, then the current flowing throughthe spin-orbit torque wiring generates heat. If heat is applied to thefirst ferromagnetic metal layer, then the stability of the magnetizationof the first ferromagnetic metal layer tends to deteriorate, andunexpected magnetization rotations or the like can sometimes occur. Ifthis type of unexpected magnetization rotation occurs, then a problemcan arise in which recorded information is rewritten. In other words, inorder to avoid unexpected magnetization rotation, it is preferable thatthe current density of the electric current flowing through thespin-orbit torque wiring is prevented from becoming too large. Providedthe current density of the electric current flowing through thespin-orbit torque wiring is less than 1×10 A/cm², at least magnetizationrotations caused by generated heat can be avoided.

In the case of a magnetization rotation method in which an “STT and SOTcombination” structure is used for the magnetoresistance effect elementof the present disclosure, an electric current may first be applied tothe power supply for the spin-orbit torque wiring, with an electriccurrent then subsequently applied to the power supply for themagnetoresistance effect element.

The SOT magnetization rotation step and the STT magnetization rotationstep may be performed simultaneously, or the SOT magnetization rotationstep may be performed first, and the STT magnetization rotation stepthen performed thereafter. In other words, in the magnetoresistanceeffect element portion 100 illustrated in FIG. 13, electric currents maybe supplied simultaneously from the first power supply 110 and thesecond power supply 120, or an electric current may first be suppliedfrom the second power supply 120, and then an electric current suppliedfrom the first power supply 110 thereafter, but in order to morereliably obtain a magnetization rotation assist effect using SOT, it ispreferable that an electric current is first applied to the power supplyfor the spin-orbit torque wiring, and then an electric current isapplied to the power supply for the magnetoresistance effect element. Inother words, it is preferable that an electric current is first suppliedfrom the second power supply 120, and subsequently, an electric currentis supplied from the first power supply 110.

DESCRIPTION OF THE REFERENCE SIGNS

-   1: Second ferromagnetic metal layer-   2: Spin-orbit torque wiring-   10: Substrate-   20: Magnetoresistance effect element-   21: First ferromagnetic metal layer-   22: Non-magnetic layer-   23: Second ferromagnetic metal layer-   23′: Connection portion (on the side of the second ferromagnetic    metal layer)-   55-   24: Cap layer-   24′: Connection portion (on the side of the cap layer)-   30: Wiring-   40, 50, 51, 52: Spin-orbit torque wiring-   40B: Connection portion-   40′: Connection portion (on the side of the spin-orbit torque    wiring)-   41, 41A, 41B: Spin current generation portion-   42A, 42B, 42C: Conductive portion-   100, 200, 300: Magnetoresistance effect element-   101: Spin current magnetization rotational element-   I: Electric current-   S⁺: Upward-directed spin-   S⁻: Downward-directed spin-   M₂₁, M₂₃: Magnetization-   I₁: First current path-   I₂: Second current path-   110: First power supply-   120: Second power supply

1. A spin current magnetization rotational element comprising: aferromagnetic metal layer having a variable magnetization direction, andspin-orbit torque wiring which extends in a direction that intersects adirection perpendicular to a surface of the ferromagnetic metal layer,and is connected to the ferromagnetic metal layer, wherein a spinresistance of a connection portion of the spin-orbit torque wiring thatis connected to the ferromagnetic metal layer is larger than a spinresistance of the ferromagnetic metal layer, and the spin-orbit torquewiring has a side wall connection portion that contacts a portion of aside wall of the ferromagnetic metal layer.
 2. The spin currentmagnetization rotational element according to claim 1, wherein thespin-orbit torque wiring layer has a spin current generation portionformed from a material that generates a spin current, and a conductiveportion, and a portion of the spin current generation portionconstitutes the connection portion.
 3. The spin current magnetizationrotational element according to claim 2, wherein an electricalresistivity of the conductive portion is not higher than an electricalresistivity of the spin current generation portion.
 4. The spin currentmagnetization rotational element according to claim 2, wherein the spincurrent generation portion is formed from a material selected from thegroup consisting of tungsten, molybdenum, niobium, and alloys containingat least one of these metals.
 5. A magnetoresistance effect elementcomprising the spin current magnetization rotational element accordingto claim 1, another ferromagnetic metal layer having a fixedmagnetization orientation, and a non-magnetic layer sandwiched betweenthe another ferromagnetic metal layer and the ferromagnetic metal layer.6. The magnetoresistance effect element according to claim 5, whereinthe another ferromagnetic metal layer is positioned below theferromagnetic metal layer in the stacking direction.
 7. Magnetic memorycomprising a plurality of the magnetoresistance effect elementsaccording to claim
 5. 8. A magnetoresistance effect element comprisingthe spin current magnetization rotational element according to claim 2,another ferromagnetic metal layer having a fixed magnetizationorientation, and a non-magnetic layer sandwiched between the anotherferromagnetic metal layer and the ferromagnetic metal layer.
 9. Amagnetoresistance effect element comprising the spin currentmagnetization rotational element according to claim 3, anotherferromagnetic metal layer having a fixed magnetization orientation, anda non-magnetic layer sandwiched between the another ferromagnetic metallayer and the ferromagnetic metal layer.
 10. A magnetoresistance effectelement comprising the spin current magnetization rotational elementaccording to claim 4, another ferromagnetic metal layer having a fixedmagnetization orientation, and a non-magnetic layer sandwiched betweenthe another ferromagnetic metal layer and the ferromagnetic metal layer.11. The magnetoresistance effect element according to claim 8, whereinthe another ferromagnetic metal layer is positioned below theferromagnetic metal layer in the stacking direction.
 12. Themagnetoresistance effect element according to claim 9, wherein theanother ferromagnetic metal layer is positioned below the ferromagneticmetal layer in the stacking direction.
 13. The magnetoresistance effectelement according to claim 10, wherein the another ferromagnetic metallayer is positioned below the ferromagnetic metal layer in the stackingdirection.
 14. Magnetic memory comprising a plurality of themagnetoresistance effect elements according to claim 6.